The pyramids of Egypt have fascinated people ever since they were built. The Step Pyramid at Saqqara started things off around 2650 B.C. Later came the iconic pyramids of Giza. What’s often forgotten, however, is that pyramid construction continued for more than a thousand years and there are at least 138 built to house the remains of pharaohs and queens. More are still being discovered. Last year, satellite imagery revealed seventeen previously unknown pyramids.

The later pyramids of Egypt tend to be overlooked, and it’s easy to see why considering the sad state of most of them. Just take a look at this photo of the pyramid of Senusret II (ruled 1895-1878 B.C.) and photographed by Jon Bodsworth. Like a lot of later pyramids, it was made of mud bricks instead of stone blocks to save money, and that’s why it’s a giant sad lump today – an interesting lump, though.

The interior tunnels are still intact and archaeologists discovered the nearby village where the workmen lived. Contrary to popular belief, slaves didn’t construct the pyramids. Actually, it was trained craftsmen and farmers who didn’t have any other work to do when their fields were underwater during the annual flooding of the Nile.

Senusret II was part of the 12th Dynasty, a high point in Egyptian power and civilization. It’s strange then that pyramids were in decline. You can see several of these pyramids at Dahsur, not far from Saqqara and an easy day trip from Cairo. One is the Black Pyramid of Amenemhat III (ruled 1842-1797 B.C.). It started to collapse almost immediately so he had to build a second one at the Faiyum Oasis near a giant temple to the crocodile god Sobek. This site reopened last year.

%Gallery-155699%The experimentation with cheaper building methods may have started with Senusret I (ruled 1962-1928 B.C.). Instead of a solid geometric shape, the builders first constructed a network of walls crisscrossing each other and dividing the pyramid into 32 parts. These were then filled with loose stone. A smooth limestone facing was put over the whole thing. It sounded good in theory, but it’s another sad lump today.

Perhaps as a compensation for the cheap building styles, the later pyramids had elaborate tricks to stop tomb robbers: dead end tunnels sealed with thick stones; interior chambers made of quartzite, the hardest substance worked in Ancient Egypt; elaborately sealed rooms that contained nothing; and sarcophagi as big as the rooms that held them in order to deny robbers room to work.

Sadly, none of these tricks worked and the pharaohs eventually resorted to hidden underground tombs in places like the Valley of the Kings. After the 12th and 13th dynasties, pyramids went out of fashion. Many of the 13th dynasty rulers didn’t bother building one at all. Only a few were made by later dynasties. The last pyramid made for a pharaoh was for Ahmose I around 1525 B.C. It’s a pile of rubble now that barely measures 30 feet high. Much later, pyramids briefly became fashionable in the Sudan.

The pyramid was dead, and last year, so was Egypt’s tourism industry. It’s been gradually rebuilding itself, though. Cruise lines are returning, as are independent travelers. The tourist sights remained mostly unaffected by the unrest and there’s not much trouble outside of a few spots in Cairo.

Visitors will have more to see with six tombs at Giza having reopened and Egyptologists hard at work uncovering more ancient wonders. Many of the later pyramids haven’t been excavated and while all the ones that have been explored were plundered by tomb robbers centuries ago, there’s always a chance that the treasure of a pharaoh remains hidden inside one of them.